Abstract: To obtain robot's locomotion mechanisms which have good passive adaptability to rugged unstructured terrain and strong obstacle-surmounting capabilities to regular obstacles such as steps and ditches,the track is introduced into the rocker-type robot mobile system.Various configurations of the rocker-type track suspensions are obtained through adding arm-tracks and fixing joint angles,and their characteristics are analyzed.According to the unstructured terrain environments and the explosive gas atmosphere environment of underground coal mine,a rocker-type tracked mobile system using a symmetrical W-shaped track suspension is presented,and the mobile platform prototype is developed.Obstacles-surmounting capabilities of this mobile system,such as anti-overturning,channel-crossing,stair-climbing,down-stair,are analyzed.The capability analysis and test results indicate that the platform is of good adaptability to complex unstructured terrains and of strong obstacles-surmounting capabilities,and it can climb up a 100 mm-high step,climb down a 450 mm-high step,and cross a 260 mm-wide ditch.